The present invention relates generally to satellite communication systems, and more particularly, to a communication system and processor embodying a code division multiple access (CDMA) code address data routing method.
The assignee of the present invention manufactures and deploys satellites that orbit the earth and which carry communication equipment. Conventional on-board processors process data communicated by way of the satellite communication equipment to demodulate, decode and individually interpret an address header. It would be desirable for the processor to not require address header processing. It would be desirable for routing to be performed based on a CDMA code. ATandT VoiceSpan has conceived a CDMA on-board processor, but it is not believed to utilize a CDMA spreading code as the router destination address.
It is an objective of the present invention to provide for a communication system and processor embodying a code division multiple access (CDMA) code address data routing method.
To meet the above and other objectives, the present invention provides for a communications system and a method that does not implement address header demodulation, decoding or interpretation to communicate. Instead, a data routing process is performed based on the assignment of one or more codes corresponding to a destination beam. In particular, data routing is performed based on a CDMA code. The communications system and method allow simplified processing of the data address and routing of the data received by the communications system on-board the satellite.
The present invention may be advantageously employed in a satellite-based communication or data routing system. In addition, the present invention may be used in terrestrial fiber router applications, for example.
An exemplary communication system comprises a satellite having a multibeam communication system disposed thereon. A plurality of ground-based user terminals 14 communicate with each other by way of the multibeam communication system. A network control center controls the multibeam communication system and communicates by way of the communication system with the user terminals, and wherein the network control center transmits status messages to the multibeam communication system and user terminals that assign a unique CDMA code to each destination beam address. Each transmitting user terminal utilizes a spreading code appropriate for the destination downlink beam in which the recipient terminal is located to spread and transmit messages destined for the recipient terminal. The communication system on-board the satellite removes the unique CDMA code used as the destination beam address as part of the on-board routing function. The despread downlink signal can be formatted so that it is readable by all terminals in the downlink beam or uniquely addressed to individual terminals within the beam. Addressing of messages to individual terminals within the destination beams may be done with additional CDMA codes to uniquely identify the intended recipient terminal or it may be done with TDM headers or FDM frequency assignments as appropriate for the signals to which the destination beam CDMA code is applied.
An exemplary data routing method comprises the following steps. Status messages are generated at the network control center that assign a unique CDMA code to each destination beam address. The network control center transmits the status messages to the user terminals. Each user terminal obtains an appropriate code address from the status messages, preferably during user registration and authentication. Each transmitting user terminal uses a spreading code associated with the code address that is appropriate for the downlink beam in which the recipient terminal is located to selectively spread and transmit messages destined for it. A recipient terminal further demodulates and decodes the downlink signal to identify messages addressed to it. A reference signal may be transmitted from the network control center to aid power and code time synchronization at the user terminals.